A San Francisco-based hedge fund has filed a lawsuit against Theranos Inc, accusing the blood testing company of using fraudulent methods to attract an investment of nearly $100 million. The hedge fund, Partner Fund Management LP (PFM), filed the lawsuit in the Delaware Court of Chancery on Monday afternoon, a letter to the hedge fund's investors said. 'Through a series of lies, material misstatements, and omissions, the defendants engaged in securities fraud and other violations by fraudulently inducing PFM to invest and maintain its investment in the company,' said the letter, which was reviewed by Reuters.